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Synthesis and characterization of novel side‐chain liquid crystalline polycarbonates, 5. Mesophase characterization of side‐chain liquid crystalline polycarbonates with tails of different lengths
Author(s) -
Jansen John C.,
Addink Rudolf,
te Nijenhuis Klaas,
Mijs Wim J.
Publication year - 1999
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19990601)200:6<1473::aid-macp1473>3.0.co;2-2
Subject(s) - side chain , polymer , mesophase , glass transition , monolayer , polymer chemistry , polycarbonate , liquid crystal , materials science , thermal stability , alkoxy group , crystallography , chemistry , phase (matter) , organic chemistry , composite material , alkyl , nanotechnology , optoelectronics
The mesomorphic properties and thermal stability of side‐chain LC polycarbonates with alkoxyphenyl benzoate side groups having a short spacer and alkoxy tails ranging from 1 to 8 carbon atoms were studied by DSC, X‐ray diffraction and polarized light optical microscopy. All polymers have a smectic A structure. Mesogens having short tails organize preferably in a monolayer structure, and mesogens having long tails in a double layer structure. A sharp increase in the clearing temperatures and enthalpies as a function of tail length was observed. No clear relation between the tail length and the glass transition temperature was found. Both the T g and the clearing temperature show a strong dependence on the molecular weight. Up to about M w = 20 000 a rapid increase in phase transition temperatures with increasing molecular weight was observed, eventually levelling off to a constant maximum value. The LC polycarbonates were found to be thermally stable up to about 200°C. At higher temperatures, random chain scission, resulting in a rapid decrease in molecular weight, and unzipping, resulting in the formation of a five‐membered cyclic carbonate, are the main initial degradation mechanisms. The degraded polymers have lower transition temperatures than the original ones.